Circuit breaker having a thermally responsive latching member

Abstract

A circuit breaker is provided with a thermally responsive latching member connected in circuit between a load terminal and a movable contact. A mounting member, holding a portion of the latching member adjacent one end thereof, is pivotally mounted in the circuit breaker housing. A U-shaped field piece is affixed to the mounting member with legs of the piece extending at both sides and toward the latching member, and toward an armature spaced on the opposite side of the latching member. The armature has its associated armature spring provided with an annular boss which is adapted to fit within a locating hole in the latching member. The field piece is adapted to intercept lines of flux of a magnetic field created by a predetermined amount of current flowing through the latching member to attract the armature to rotate the latching member thereby disengaging a latching surface of the latching member from a trip arm, releasing the trip arm for movement to a tripped position. A mounting spring bears against the housing and urges the field piece against a support member, and further urges the armature spring against the latching member and positions the boss into the locating hole.

What is claimed is: 
     
       1. A circuit breaker including in combination a housing of insulating material; a fixed contact mounted in said housing;   a movable handle mounted in said housing;   a contact carrier with a movable contact thereon and pivotally engaging said handle at a pivot point;   a trip arm pivotally mounted in said housing;   an overcenter spring connected between said contact carrier and said trip arm urging said contact carrier against said handle;   said handle, contact carrier, and overcenter spring forming an overcenter arrangement for closing said contacts when the spring is on one side of said pivot point and for opening said contacts when the spring is on the other side of said pivot point;   a load terminal mounted in said housing;   a thermally responsive latching member connected in circuit between said load terminal and said movable contact, said latching member having a locating hole therewithin;   an armature;   an armature spring affixed to said armature and having a free end provided with an annular boss adapted to fit within said locating hole;   a mounting member holding the thermally responsive latching member at a portion thereof adjacent to one end;   said mounting member being pivotally mounted in said housing at a pivotal connection;   a U-shaped field piece affixed to said mounting member with legs of said piece extending at both sides and toward said thermally responsive latching member and facing said armature;   a support member mounted in said housing and bearing against said field piece; and   a mounting spring bearing against the housing and urging said field piece against said support member whereby said pivotal connection, said support member, said field piece, and said mounting member in combination hold the portion of the thermally responsive latching member adjacent said one end fixed with respect to the housing, said thermally responsive latching mechanism being rotatable about the pivotal connection against the urging of said mounting spring;   said thermally responsive latching member having a latching surface adjacent the opposite end thereof engaging said trip arm and maintaining said trip arm in a set position when said contacts are closed, with said overcenter spring urging said trip arm toward a tripped position;   said thermally responsive latching member bending in response to a predetermined current condition to move said opposite end of the thermally responsive latching member and disengage said latching surface from said trip arm releasing said trip arm for movement to the tripped position;   said U-shaped field piece being adapted to intercept lines of flux of a magnetic field created by a predetermined amount of current flowing through said thermally responsive latching member to attract said armature against said latching member to rotate said latching member thereby disengaging said latching surface from said trip arm, releasing said trip arm for movement to said tripped position; and   movement of the trip arm to the tripped position moving the overcenter spring to the other side of said pivot point causing said contacts to open.   
     
     
       2. The circuit breaker as recited in claim 1 wherein said mounting spring further urges said armature spring against said latching member, and positions said annular boss into said locating hole. 
     
     
       3. The circuit breaker as recited in claim 2 wherein said boss of said armature spring seats within said locating hole. 
     
     
       4. A circuit breaker in accordance with claim 3 wherein said thermally responsive latching member is a unitary structure consisting of a generally flat elongated thermostat element.